1. Field of the Invention
The present invention relates to a process for producing a cooked noodle product packaged for ambient temperature distribution that keeps pleasant organoleptic quality such as texture for a long period of time without the aid of additives.
2. Description of the Related Art
It is said that boiled noodles are most palatable with highest viscoelasticity and a firm and bouncy texture immediately after boiled. With time after that, boiled noodles loose the texture.
To overcome this problem, it has been proposed to add transglutaninase to dough comprising cereal flour and other raw materials (see JP-A-6-14733) or to add transglutamninase and gliadin or glutenin to such noodle dough (see JP-A-10-276695).
However, the recent consumers tend to avoid foodstuffs containing additives.
One of the latest trends in food is the demand for convenience. A variety of pre-cooked foods that can be easily and quickly served simply by, for example, pouring hot water or microwaving are now widespread. The trend to convenience is seen for noodle products as well.
Before cooked noodle can be subjected to ambient temperature distribution, it is necessary to control growth of microorganisms. To address this problem, it is known that cooked noodles as well as other cooked foodstuffs can be sterilized by heating under pressure after packing as in retort sterilization technology.
However, heat/pressure sterilization of cooked noodles after packing is disadvantageous in that the tissue of the noodle is changed while heated under pressure as packed in a closed container. Seeing that a texture to the teeth is of great significance for noodle products, the change of noodle's tissue, which heavily affects the texture, is a serious problem. It has therefore been demanded to establish a sterilization technique for cooked noodles that can replace the post-packaging heat/pressure sterilization to achieve microorganism control without impairing the tissue of the noodles.
Japanese Utility Model 3024090 teaches a method of producing cooked noodles which solves the microorganism control problem without involving post-packaging heat/pressure sterilization that may change the tissue of cooked noodles. In the method, a UV sterilized tray is filled with cooked noodles, sterilized in a closed chamber with pressurized steam at 100° C. or higher, preferably 130 to 140° C., and sealed in a clean booth. The step of sterilization is carried out either continuously for consecutive several tens of seconds to several tens of minutes or by repeating about 6 to 8 cycles of sterilization for 6 to 10 seconds per cycle.
According to this method, however, the tray in which sterilized noodles are to be put must previously be UV sterilized so that a UV sterilizer, which is a large-sized apparatus, is required. Moreover, the method involves troublesome steps. Because food trays are made of, for the most part, organic polymer materials, there is a fear that the organic polymer material undergoes radical reaction on UV irradiation, resulting in forming carcinogenic chemicals or endocrine-disrupting chemicals.
When sterilized continuously for several tens of seconds to several tens of minutes as in the above-described method, cooked noodles lose firmness to the teeth and become overly soft. When intermittently given about 6 to 8 cycles of sterilization for 6 to 10 seconds each, safety cannot be secured particularly where the number of initial microbial cells is great.
A food processing method including filling a container with a foodstuff, heat/pressure sterilizing the container and contents, and aseptically sealing the container (see JP-A-4-370081) is also known effective for preserving cooked foods.
Heat/pressure sterilization is generally a high temperature/high pressure treatment with steam at 100° C. or higher. To carry out the method of JP-A4-370081, after the container and contents are heat/pressure sterilized in a chamber of a heat/pressure sterilizer, the inner pressure of the chamber should be released to atmospheric pressure by venting before sealing.
When the chamber of a heat/pressure sterilizer is released to the atmosphere after sterilization, it has been the practice mostly followed to vent the chamber at a time in nature of the structure of the equipment and the like. Such a manner of venting is disadvantageous in that the food bursts out of the container to contaminate the opening of the container to be sealed, which results in not only short weight packages but incomplete sealing. This occurs with solid foods cooked by stewing, boiling, steaming or browning in oil or oiled solid foods, especially those cooked by stewing, boiling or steaming.
Some long-life foods such as long-life noodles that have recently been developed enjoy long term preservability secured by their lowered pH. In order to guarantee such preservability, not only the surface but also the inside of a foodstuff must be adjusted to a low pH when microorganisms are expected to be there. To adjust the pH of a foodstuff even to the inside makes of necessity the inside of the foodstuff sour in taste and smell. Such sour taste and smell are not favorable for palatability and flavor of many foods.
To overcome these problems, JP-A-5-15330 discloses a method of producing a preservable boiled noodle product comprising preparing dough containing glucono-delta-lactone, cutting sheeted dough into noodle strands, boiling the noodles, dipping the boiled noodles in a mixed aqueous solution containing adipic acid and a sweetener to adjust the pH of the noodles to 4.5 or lower, packing the noodles in a film container, and heat sterilizing the package. JP-A-9-248148 proposes a preservative for boiled noodles comprising an acid as a pH adjustor, a sugar, and an animal or vegetable protein hydrolyzate. However, the method and the preservative cannot be seen as satisfactory.